The present invention relates to a circuit sheet and the components thereof having a three-dimensional structure and a method for manufacturing the same. These circuit sheet and components are used in display panels or operation panels for household electrical appliances, and switching parts for mobile telephones, portable information devices, or interior parts of motor vehicles.
In such a three-dimensionally formed circuit sheet, circuit patterns has been conventionally formed on a three-dimensional film substrate by a photographic method (ultraviolet exposure method) or a plating method that are typically used for manufacturing printed wiring boards.
Japanese Laid-Open Patent Publication No. 9-319068 discloses a method for manufacturing a three-dimensionally formed circuit component using a photographic method. According to the manufacturing method, a photomask is formed using two-dimensional and three-dimensional masks, and a three-dimensionally formed substrate previously subjected to plating and resist treatments is prepared. Then, the three-dimensionally formed substrate is exposed and developed in a state wherein the photomask is in close contact with the three-dimensionally formed substrate, to form an electric-circuit pattern on the three-dimensionally formed substrate.
Japanese Laid-Open Patent Publication No. 9-129995 discloses a method for manufacturing a three-dimensionally formed circuit component using a plating method. According to the manufacturing method, a circuit pattern consisting of an electrically conductive layer is formed by printing on the surface of a flatly molded electrical insulating layer, followed by bending the molded electrical insulating layer into a three-dimensional shape. Then, a metal layer is formed on the electrically conductive layer by plating.
Japanese Laid-Open Patent Publication No. 2001-36240 describes a transferring method for forming a circuit pattern by thermally transferring a film, on which a circuit pattern is formed of a copper foil or the like, onto a substrate.
However, the formation of a circuit sheet using photographic or plating methods requires a number of chemicals including an etchant and a plating solution in processing steps such as a step of roughing the surface of the resin. Since wastes from such chemicals cause significant damage to the global environment, environmental protection for a manufacturing process and the control of the used chemicals are complicated.
In the transferring method, a transfer film having a circuit pattern must be previously fabricated. In addition, since the transfer of the film onto the curved or corner portions of the substrate is difficult, the shape of the substrate on which a circuit can be formed is limited.
In the circuit component disclosed in Japanese Laid-Open Patent Publication No. 2001-36240, a resin film and a circuit pattern are three-dimensionally formed individually, and are integrated by laminating in a mold. In this case, a number of molding steps are required leading to increase in manufacturing costs.
The present invention has been devised for solving such conventional problems, and an objective of the present invention is to provide a three-dimensionally formed circuit sheet and components that can be manufactured through a simple process without breakage of circuit patterns, and a method for manufacturing the same.